VrayRT GPU issues

[Algehov]

Im still having quite abit of trouble getting RT for GPU to be usable or reliable. I was under the impression that most stuff where fixed when rendering on the GPU now (and the main issue is to fit everything on the GPU memory rather than not rendering properly).

However, we got a scene where we can test a bunch of vray-related stuff for example checking if a new vray version renders predictably in our pipeline, or to benchmark/troubleshoot computers.
It renders just fine on RT CPU, but when swapping to GPU quite a lot starting to look wierd.

This is tested on vray version is 3.10.01 official build, and Maya 2015 (2016 renders the same errors however). And on a Quadro K5200. I havnt tried the latest nightly yet, but I cant see any direct changes in the release notes that would affect this.



I sort of understand why the floor renders strange, as that shader is built with a singleSwitch node that randomizes some wood textures. I assume singleSwitch does not work on the GPU yet?
However the skin shader, normal fog color, 2d displacement, translucency with fog color, 2 sided mtl, hair shader and textures rendered manipulated with a ramp through a rgbToHsv all seems to render incorrectly.
Im surprised the substance file renders just fine, tho.

Here is an image sort of explaning what the different stuff is (it was not made for this purpose so it might be abit brief).




If you need to take a look at the scene you can download it here:
https://mega.nz/#!i4gm0brI!WARbpUIHq...s1stFSyRlWO1x4

And just remove the xGen fur for quicker testing Takes abit of time compiling the geometry.

Thanks in advance,
Simon

[yolov]

Looking at the scene now to identify what is not supported and update you on what has changed since 3.1 and what we'll be able to do in the near future.

[Algehov]

Thank you!
I noticed that the substance file was missing from the scene I uploaded, but since it rendered just fine I assume thats okay.

[yolov]

Yes, there's other things to look into anyway

[yolov]

Apart from the single switch, we currently don't support remap-ramps and blend colors in the glossiness attribute of the VRayMtl, and we only support bitmaps for bump, along with baked procedural textures (but remap or blend nodes will not work for bump). We'll see what can be done about this.
Also we don't support the translucency of the VRayMtl, but there's already requests for this, I'll up it in priority.
And we don't support the skinMtl for the moment.

Just a note - the latest vray builds print warnings for unsupported bump textures.

[Algehov]

Oh I see. Having support for remap-ramps in glossiness would be very good, since probably over 90% of our shaders on a daily basis uses that. But that explains why I never seems to get predictable results when trying out RT with gpu.
Any idea whats going on with with no fog color, the hair shader, and why there's a slightly whiter "ball" in the 2sided mtl? It also looks like the sun is not being rendered in reflections (only in specular perhaps?)

Thanks for a quick reply anyway. Keep me updated when it might be fixed

[yolov]

I'll probably look at the 2sided on monday, but I'll keep you posted on any progress we have on those features.

[yolov]

Opacity for submaterials in 2sidedMtl is not supported on the GPU, that's where the difference come from. It's already on our to-do list.